Self-Tuning Underwater Image Restoration

A self-tuning image restoration filter based on a simplified version of the Jaffe-McGlamery underwater image formation model is presented. Optimal values of the filter parameters are estimated automatically for each individual image by optimizing a quality criterion based on a global contrast measure. The simplified model is ideally suitable for diffuse-light imaging with limited backscatter, but qualitative tests show good performance in a variety of imaging conditions. In addition, quantitative tests with a large number of frames from six real mission videos indicate a substantial performance improvement when restoration is used as a preprocessor for a classifier detecting man-made objects in unconstrained subsea videos     

Computer vision techniques for quantifying, tracking, andidentifying bioluminescent plankton

This paper applies computer vision techniques to underwater video images of bioluminescent biota for quantifying, tracking, and identification. Active contour models are adapted for computerized image segmentation, labeling, tracking, and mapping of the bioluminescent plankton recorded by low-light-level video techniques. The system automatically identifies luminous events and extracts features such as duration, size, and coordinates of the point of impact, and uses this information to taxonomically classify the plankton species. This automatic classification can aid oceanographic researchers in characterizing the in situ spatial and temporal relationships of these organisms in their underwater environment. Experiments with real oceanographic data are reported. The results indicate that the approach yields performance comparable to human expert level capability. Furthermore, because the described technique has the potential to rapidly process vast quantities of video data, it may prove valuable for other similar applications     

水下光学无线通信的海水信道特性研究

提出了将具有比声学高达几倍的数据通信速率,良好的安全性和隐蔽性的光学无线通信技术应用于海军、海洋科学研究和水下工程等领域,实现高速率的水下无线通信技术实现海量数据的信息交换.基于生物光学特性的水下光学信道模型,建立了水下光学通信系统性能分析方法.并对基于发光二极管(LED)的水下光学无线通信系统进行了仿真,其结果表明所建立的方法可以进行各种海域水质环境的模拟,便于时水下光学无线通信系统性能进行预测评估,为水下光学无线通信系统的设计方案的评估提供了依据.     

A voting-based approach for fast object recognition in underwateracoustic images

This paper describes a voting-based approach for the fast automatic recognition of man-made objects and related attitude estimation in underwater acoustic images generated by forward-looking sonars or acoustic cameras. In general, the continuous analysis of sequences of images is a very heavy task for human operators and this is due to the poor quality of acoustic images. Hence, algorithms able to recognize an object on the basis of a priori knowledge of the model and to estimate its attitude with reference to a global coordinate system are very useful to facilitate underwater operations like object manipulation or vehicle navigation. The proposed method is capable of recognizing objects and estimating their two-dimensional attitude by using information coming from boundary segments and their angular relations. It is based on a simple voting approach directly applied to the edge discontinuities of underwater acoustic images, whose quality is usually affected by some undesired effects such as object blurring, speckle noise, and geometrical distortions degrading the edge detection. The voting approach is robust, with respect to these effects, so that good results are obtained even with images of very poor quality. The sequences of simulated and real acoustic images are presented in order to test the validity of the proposed method in terms of average estimation error and computational load     

A comparison of inter-frame feature measures for robust objectclassification in sector scan sonar image sequences

This paper presents an investigation of the robustness of an inter-frame feature measure classifier for underwater sector scan sonar image sequences. In the initial stages the images are of either divers or remotely operated vehicles (ROV's). The inter-frame feature measures are derived from sequences of sonar scans to characterize the behavior of the objects over time. The classifier has been shown to produce error rates of 0%-2% using real nonnoisy images. The investigation looks at the robustness of the classifier with increased noise conditions and changes in the filtering of the images. It also identifies a set of features that are less susceptible to increased noise conditions and changes in the image filters. These features are the mean variance, and the variance of the rate of change in time of the intra-frame feature measures area, perimeter, compactness, maximum dimension and the first and second invariant moments of the objects. It is shown how the performance of the classifier can be improved. Success rates of up to 100% were obtained for a classifier trained under normal noise conditions, signal-to-noise ratio (SNR) around 9.5 dB, and a noisy test sequence of SNR 7.6 dB     

Stereovision imaging on submersible platforms for 3-D mapping of benthic habitats and sea-floor structures

We investigate the deployment of a submersible platform with stereovision imaging capability for three-dimensional (3D) mapping of benthic habitats and other sea-floor structures over local areas. A complete framework is studied, comprising: 1) suitable trajectories to be executed for data collection; 2) data processing for positioning and trajectory followed by online frame-to-frame and frame-to-mosaic registration of images, as well as recursive global realignment of positions along the path; and 3) 3D mapping by the fusion of various visual cues, including motion and stereo within a Kalman filter. The computational requirements of the system are evaluated, formalizing how processing may be achieved in real time. The proposed scenario is simulated for testing with known ground truth to assess the system performance, to quantify various errors, and to identify how performance may be improved. Experiments with underwater images are also presented to verify the performance of various components and the overall scheme.     

三锚浮标系统研究

海洋浮标是一种现代化的海洋观测设施。它具有全天候、全天时稳定可靠的收集海洋环境资料的能力,并能实现数据的自动采集、自动标示和自动发送。海洋浮标与卫星、飞机、调查船、潜水器及声波探测设备一起,组成了探测海洋奥秘的主体监测系统。论文详细阐述了水面浮标采用的新型三锚系留系统的组成、优点、以及克服的技术难题。     

A Novel Method for Real-Time Monitoring of Channel Siltation Based on Bistatic Scattering Theory

Monitoring the thickness changes of channel siltation is paramount in safeguarding navigation and guiding dredging.This paper presents a novel method for realizing the field monitoring of channel siltation in real time.The method is based on the bistatic scattering theory and concerned more with the receiving and processing of multipath signal at high-frequency and small grazing angle.By use of the multipath propagation structure of underwater acoustic channel,the method obtains the silt thickness by calculating the relative time delay of acoustic signals between the direct and the shortest bottom reflected paths.Bistatic transducer pairs are employed to transmit and receive the acoustic signals,and the GPS time synchronization technology is introduced to synchronize the transmitter and receiver.The WRELAX (Weighted Fourier transform and RELAX) algorithm is used to obtain the high resolution estimation of multipath time delay.To examine the feasibility of the presented method and the accuracy and precision of the developed system,a series of sea trials are conducted in the southwest coast area of Dalian City,north of the Yellow Sea.The experimental results are compared with that using high-resolution dual echo sounder HydroBoxTM,and the uncertainty is smaller than ±0.06 m.Compared with the existing means for measuring the silt thickness,the present method is innovative,and the system is stable,efficient and provides a better real-time performance.It especially suits monitoring the narrow channel with rapid changes of siltation.     

水下碍航物信息三维可视化管理技术研究

研究了水下碍航物信息的获取、处理、显示和管理等一整套技术方法,以水下碍航物数据库为支持,实现水下碍航物数据的获取、海图碍航物信息自动入库、水下碍航物可视化编辑、元数据信息查询和空间定位等功能,并实现以图片库和模型库为支持的海图碍航物要素的三维空间表达,建立水下碍航物三维可视化管理系统平台,为海洋测绘作业人员提供全方位、一体化的技术支持和信息保障。     

基于卫星测高数据的海洋中尺度涡流动态特征检测

为了最终实现对海洋中尺度涡流(简称中尺度涡)的自动采样,首先应该发展中尺度涡动态特征识别技术。本文基于SLA(Sea Level Anomaly)数据,实现了对中尺度涡动态特征的检测算法。主要内容是制定了一个判别相邻两组SLA数据中的涡流,是否为同一涡流子在不同时刻的状态的标准,即判别下一时刻SLA数据中是否存在涡流是由上一时刻确定的被检测涡流演化而来的。通过确定这种进化关系,可以得到被检测涡流的一系列动态状态信息,例如:面积变化速率、中心移动情况以及其他情况。本算法的计算量不大,从而可以应用到实时涡流跟踪的环境中。值得注意的是,本文中的算法不仅仅局限于应用SLA数据,SSH(Sea Surface Height)等大部分反映海洋高度的数据也可以使用。     

Numerical investigation of the hydrodynamic interaction between two underwater bodies in relative motion

The hydrodynamic interaction between an Autonomous Underwater Vehicle (AUV) manoeuvring in close proximity to a larger underwater vehicle can cause rapid changes in the motion of the AUV. This interaction can lead to mission failure and possible vehicle collision. Being self-piloted and comparatively small, an AUV is more susceptible to these interaction effects than the larger body. In an aim to predict the manoeuvring performance of an AUV under the effects of the interaction, the Australian Maritime College (AMC) has conducted a series of computer simulations and captive model experiments. A numerical model was developed to simulate pure sway motion of an AUV at different lateral and longitudinal positions relative to a larger underwater vehicle using Computational Fluid Dynamics (CFDs). The variables investigated include the surge force, sway force and the yaw moment coefficients acting on the AUV due to interaction effects, which were in turn validated against experimental results. A simplified method is presented to obtain the hydrodynamic coefficients of an AUV when operating close to a larger underwater body by transforming the single body hydrodynamic coefficients of the AUV using the steady-state interaction forces. This method is considerably less time consuming than traditional methods. Furthermore, the inverse of this method (i.e. to obtain the steady state interaction force) is also presented to obtain the steady-state interaction force at multiple lateral separations efficiently. Both the CFD model and the simplified methods have been validated against the experimental data and are capable of providing adequate interaction predictions. Such methods are critical for accurate prediction of vehicle performance under varying conditions present in real life.     

ROV虚拟监控和动力定位系统软件分析与设计

在某型ROV控制系统的基础上扩展开发了一套具有虚拟监控(VMS)功能和动力定位(DP)功能的软件,此软件不仅能够仿真ROV的水下作业过程并且能实时对ROV的水下作业进行控制。介绍了此软件的开发过程并对软件中各组成部分以及它们之间的关系进行了详细的论述。     

Geometrical aspects of a sonar-based navigation system for underwater vehicles

A novel self-contained navigation system has been devised for underwater vehicles operating in and around offshore installations. This system matches data from a sector-scanning sonar device to a computer model of the installation. The paper begins by highlighting the existing approaches to subsea navigation before outlining the main features of the proposed system. It then concentrates on a key component of this system which is a method for calculating the position and heading of an underwater vehicle navigating in the vincinity of tubular steel structures. An iterative solution method is presented which incorporates six degree of freedom vehicle motions and this is verified in a series of laboratory experiments with various arrangements of structural members and using a commercial sonar device. The key features, applications and performance of this method are discussed. The main conclusion is that the proposed method for calculating the position and heading of an underwater vehicle contributes towards achieving an accurate and reliable subsea navigation capability.     

A New Video and Digital Camera System for Studies of the Dynamics of Microtopographic Features on Tidal Flats

A newly developed video and camera system for tidal flat microtopographic studies is presented. It consists of a SONY handy cam placed in an underwater housing mounted on a frame about 70?cm above the sediment surface. A rectangular surface area of 30?×40?cm is imaged by the camera. The camera records video sequences and/or digital images at predetermined time lapses. The total number of images is about 540, and a similar number of 10-second long video sequences can be recorded. The camera is programmed with a PC before deployment, and the total deployment time depends on the time lapse between recordings. The camera is connected to an external power supply (12?volt), and a halogen projector pointing towards the sediment surface ensures that the system is operable on a 24-hours scale. The system has been tested in the Danish Wadden Sea. It has proved to be a very useful tool in studies of topographic effects of erosion and deposition sequences, and for studies of benthic organisms-sediment interactions. The test site was further equipped with sensors for water and seabed measurements, which proved to be indispensable regarding the interpretation of recorded image time-series.     

A New Video and Digital Camera System for Studies of the Dynamics of Microtopographic Features on Tidal Flats

A newly developed video and camera system for tidal flat microtopographic studies is presented. It consists of a SONY handy cam placed in an underwater housing mounted on a frame about 70 cm above the sediment surface. A rectangular surface area of 30 ×40 cm is imaged by the camera. The camera records video sequences and/or digital images at predetermined time lapses. The total number of images is about 540, and a similar number of 10-second long video sequences can be recorded. The camera is programmed with a PC before deployment, and the total deployment time depends on the time lapse between recordings. The camera is connected to an external power supply (12 volt), and a halogen projector pointing towards the sediment surface ensures that the system is operable on a 24-hours scale. The system has been tested in the Danish Wadden Sea. It has proved to be a very useful tool in studies of topographic effects of erosion and deposition sequences, and for studies of benthic organisms-sediment interactions. The test site was further equipped with sensors for water and seabed measurements, which proved to be indispensable regarding the interpretation of recorded image time-series.     

Robust control for underwater vehicle systems with time delays

A robust control scheme is presented for controlling systems with time delays. The scheme is based on the Smith controller and the LQG/LTR (linear quadratic Gaussian/loop transfer recovery) methodology. The methodology is applicable to underwater vehicle systems that exhibit time delays, including tethered vehicles that are positioned through the movements of a surface ship and autonomous vehicles that are controlled through an acoustic link. An example, using full-scale data from the tethered vehicle ARGO, demonstrates the developments     

海底底质声学原位测量电路控制系统研究

介绍了一种液压驱动贯入式海底沉积声学原位测量系统的电路控制单元的研究实现过程,以及该控制单元在南海北部海底沉积声学调查中的应用。该电路控制单元以Cortex-A8处理器为核心,集成大容量FLASH存储器,与单片机接口控制板进行串口通讯,实现对声学发射采集单元和机械液压贯入单元的可视化控制和监测。基于该电路控制单元,海底底质声学原位测量系统兼具自容式和在线式两种工作模式,可自容记录或实时采集声学原位测量单元在海底的工作状态数据、海底沉积物声速和声衰减系数等声学特性数据。该声学原位测量系统的实验室联调及南海海试结果表明,使用该电路控制单元对海底底质声学测量过程的监测与控制是有效的,对精确获取海底底质的原位声学特性有重要作用,可以促进海底底质声学原位测量系统的产品化。     

Teleprogramming for subsea teleoperation using acousticcommunication

This paper considers the performance of subsea intervention tasks from an unmanned untethered submersible while using acoustic communications. It is argued that the low bandwidth and high delay imposed by acoustic modems makes it unwise to adopt conventional teleoperation techniques and a system is presented which permits subsea teleoperative tasks to be carried out using such limited communication resources. The described implementation employs active techniques to assist the operator both in performing actions and in recovering from those problems which will inevitably occur during real-world interaction. It provides the operator with both simulated and real visual imagery and is designed to adapt dynamically to changing bandwidth and computational resources. Experiments are described in which an operator in Philadelphia, PA, controlled a robot manipulator mounted on the JASON underwater vehicle submerged off the Massachusetts coast. All communication over this 500-km distance was via a combination of Internet and a simulated acoustic link. Analysis of the bandwidth requirements showed them to be consistent with those from acoustic subsea networks     

近海污染/生态环境自动监测装置--水质监测浮标

本文介绍了863－818支持研究的最新成果“近海污染／生态环境自动监测技术（水质监测浮标）”的功能，特点及关键技术，它利用海水营养盐现场自动分析仪和水传感器，pH，溶解氧，温度，盐度）集成自动水质监浮标，主要应用于河口地带，排污口附近海域经洋增养殖区，自动完成数据采集，处理，存储及储输，实时，连续地为水质污染监测，海洋水产养殖提供服务，同时为海综合管理和海洋科学研究提供基础数据，该成果对于我国海洋环境立体监测网的建设具有重要的意义。